WO2005042595A1

WO2005042595A1 - Butyl-type rubber with high viscosity

Info

Publication number: WO2005042595A1
Application number: PCT/CA2004/001906
Authority: WO
Inventors: Adam Gronowski; Akhtar Osman
Original assignee: Lanxess Inc.
Priority date: 2003-11-03
Filing date: 2004-11-02
Publication date: 2005-05-12
Also published as: CA2448337A1

Abstract

The present invention relates to an elastomer having repeating units derived from at least one isomonoolefin monomer, at least one diisoalkenylbenzene monomer, and optionally further copolymerizable monomers, said elastomer having a Mooney viscosity (ML 1+8&commat;125 °C according to ASTM D1646) of more than 80 units, as well as a curable composition comprising said elastomer and a shaped article manufactured from said curable composition.

Description

BUTYL-TYPE RUBBER WITH HIGH VISCOSITY

FIELD OF THE INVENTION The present invention relates to an elastomer having repeating units derived from at least one isomonoolefin monomer, at least one diisoalkenylbenzene monomer, and optionally further copolymerizable monomers, said polymer having a Mooney viscosity (ML 1+8@125 °C according to ASTM D1646) of more than 80 units as well as a curable composition comprising said elastomer and a shaped article manufactured from said curable composition.

BACKGROUND In many of its applications, isoolefin copolymers, in particular butyl rubber is used in the form of cured compounds. Rubbery copolymers of isoolefins of 4 to 7 carbon atoms, such as isobutylene, and aliphatic dienes of 4 to 14 carbon atoms, such as isoprene or butadiene, are known by the generic name of "butyl rubbers"(IIR). Butyl rubber is manufactured by copolymerizing isobutylene and isoprene in methyl chloride diluent using aluminum chloride as a catalyst. This cationic polymerization is carried out in a continuous reactor at temperatures below - 90 °C. A solution process is also known, with a C₅-C hydrocarbon as solvent and an aluminum alkylhalide catalyst. The isoprene incorporated in IIR (ca. 0.5-2.5 mol %) provides double bonds, which allow the rubber to be vulcanized with sulfur and other vulcanizing agents. Butyl rubber and its vulcanizates are characterized by impermeability to air, high damping of low frequency vibrations, and good resistance to aging, heat, acids, bases, ozone and other chemicals. These characteristics lead to the use of butyl rubber in tire inner tubes, tire curing bladders and bags, vibration insulators, roof and reservoir membranes, pharmaceutical bottle stoppers and other applications. The polymer is similar in structure to polyisobutylene and has a similar glass transition temperature, T_g, of -72 °C. A large number of methyl groups positioned along the macromolecular chains interfere mechanically with each other and reduce the speed with which the molecules respond to deformation. This explains the low rebound resilience and typical damping properties of this product. On the other hand, the relatively low mobility of the molecule segments gives butyl rubber its well-known impermeability to oxygen, nitrogen, carbon monoxide, water and other substances, which do not swell the vulcanizate. As is well known to those skilled in the art, the viscosity of elastomers is usually measured using the Mooney viscosity test. During this test, a flat, serrated disc rotates in a mass of rubber contained in a grooved cavity under pressure. The torque required to rotate the disc at 2 rpm at a fixed temperature is defined as the Mooney viscosity. Normal butyl elastomers are gel-free - that is, they are entirely soluble in hydrocarbon solvents (hexane, mineral spirits, benzene, toluene). The usual range of molecular weights of butyl rubber is 250,000 -750,000 g/mol. As with other rubbers, the Mooney viscosity of the polymer has a strong influence on the processing behavior, low viscosity grades being easier to process. However, if the compound needs fairly good dimensional stability or shape retention, the grades with higher viscosity are preferred. The usual range of Mooney viscosity values for butyl rubber is 30-50 units (ML 1+8@125 °C), depending on the grade. Bayer manufactures also a special crosslinked grade of butyl rubber under the trademark of XL- 10000™. These are isobutylene- isoprene-divinylbenzene terpolymers with Mooney viscosity typically in the range of 60-75 units (ML 1+8@125 °C). These products are often used in sealants/adhesives and in electrolytic condenser caps. For some specific applications, high-viscosity rubber is needed. For example, this is the case with soft printing rollers. The function of the rollers used in printing presses is not just to exert pressure. In fact, the rollers used in inking units in letterpresses and offset printing equipment must actually be particularly soft. However, the production of suitable rubber blends for this particular application presents a major challenge for engineers. A simple addition of large amounts of plasticizers often does not solve the problem. Low- iscosity rubbers, in particular, turn into a sticky mass upon the addition of large quantities of plasticizers, making them even more difficult to process. In the vulcanized state the compounds can undergo profound dimensional changes because plasticizers can be washed out by the oil- containing printing inks or dissolved in detergents. The result is poorer print quality, combined with higher printing costs due to frequent adjustments that have to be made to the inking system. Butyl rubber is also known to be useful in printing blankets for the dry offset cup, tube and lid printing markets. This industry prints on rigid containers including cups, tubes and pails. Properly formulated butyl rubber compounds offer optimum resistance to most UV and IR printing inks, as well as provide excellent solvent resistance. The free radical initiated polymerization of diisopropenylbenzes (DIPB's) is known. However, this free radical initiated polymerizations produced crosslinked gels. The use of an anionic technique made it possible to produce essentially linear, soluble polymer in which only one unsaturation site of each DIPB molecule was consumed. At low conversions, the aromatic ring of each pendant group carried an unreacted isopropenyl group ("Malα-omol. Chem.", 183. (2787 (1982), US. Pat. 4,499,248). Branching and crosslinking could occur at higher conversions (> 50 %). The cationic polymerization of DIPB's was found to produce polymers containing predominantly a polyindane structure ("J. Polym. Sci.", 28, 629 (1958). The molecular weight increased in a stepwise manner with time and the overall process was kinetically more akin to a polycondensation than to a conventional vinyl polymerization. The continuation of the vinyl addition beyond the dimer stage led to crosslinked products. D'Onofrio ("J. Appl. Polym. Sci." 8, 521 (1964) demonstrated that linear, high molecular weight, soluble polyindane was produced from diisopropenylbenzenes at polymerization temperature above 70 °C using a complex Lewis acid type initiating system (LiBu-TiCl₄-HCl). It was pointed out that with the use of BF₃, TiCl , SnCl₄, etc., a narrow polymerization range (70-100 °C) was necessary in order that soluble polymer was obtained. At temperatures below 70 °C crosslinked products resulted. At temperatures higher than 100 °C, the activity of the catalyst decreased. Sonnabend (US Pat, 3,004,953) claimed a direct cationic copolymerization of diisopropenylbenzenes with phenol. The process was complicated by the simultaneous occurrence of propagation and alkylation reactions, with products exhibiting branching and ultimately gelation. H. Colvin et al. described a direct cationic copolymerization of m- diisopropenylbenzene and m-dimethoxybenzene (in "New Monomers and Polymers", B. Culbertson and C. Pittman (Eds.), Plenum Press, New York 1984, 415-428). The dimethoxybenzene could be incorporated into the polymer backbone or as a pendant group. The most important variable in controlling the ratio of mono- to dialkylated dimethioxybenzene was the catalyst. The M_w of the polymer was below 50,000 g/mol and the properties were poor. Copolymers of p- or m- diisopropenylbenzene with styrene exhibited unusually high melting points and increased chemical and heat resistance (GB 850, 363). These copolymers containing at least 5 % of the difunctional monomer could be useful as moulding resins, adhesives, priniting inks and as additives for lubricating oils to raise the viscosity index of the oil. The preferred catalyst was a cationic catalyst. US Pat. 3,067,182 taught that uniform copolymers of isopropenylbenzene chloride with isobutylene could be made under cationic copolymerization conditions at temperatures below - 100 °C. Such copolymers could be readily crosslinked with amines or phenols or by adding a Friedel-Crafts catalyst to obtain cure by self- alkylation. Multi-arm star polyisobutylenes were prepared by the "arm-first" method

("Macromol. Symp.", 95, (1995) 39-56). This synthesis was accomplished by adding various linking agents ("core builders") such as p- and m- divinylbenzene and p- and m- diisopropenylbenzene (DIPB) to living PIB⁺ charges and thus obtaining a crosslinked aromatic core holding together a corona of well-defined arms. The products were characterized in terms of overall arm/core composition, molecular weight and molecular weight distribution. Star-shaped polymer, useful as viscosity modifier for lubricating oil, comprised poly(diisopropenylbenzene) as core with at least three polyisobutylene arms (EP 1099717 A). Polymerization occurred in the presence of titanium tetrachloride a d pyridine (living polymerization). Co-pending applications CA-2,386,628 and CA-2,368,646 provide a compound comprising at least one elastomeric polymer comprising repeating units derived from at least one C₄ to C isomonoolefin monomer, at least one C₄ to C₁₄ multiolefin monomer or β-pinene, at least one multiolefin cross-linking agent and at least one chain transfer agent, said polymer containing less than 15 wt.% of solid matter insoluble within 60 min in cyclohexane boiling under reflux, at least one filler and a peroxide curing system. The multiolefin cross-linking agent is a multiolefinic hydrocarbon compound. Examples of these are norbornadiene, 2-isopropenylnorbornene, 2-vinyl-norbornene, 1,3,5-hexatriene, 2-phenyl- 1,3 -butadiene, divinylbenzene, diisopropenylbenzene, divinyltoluene, divinylxylene or Ci to C ₀ alkyl-substituted derivatives of the above compounds. A co-pending application filed with the Canadian Intellectual Property Office on Aug. 05, 2003 under the attorney docket POS 1142 CA provides a method of improving reversion resistance of a peroxide curable polymer comprising at least one polymer having repeating units derived from at least one isomonoolefin monomer and at least one aromatic divinyl monomer by polymerizing the monomers in the presence of at least one m- or p-diisoalkenylbenzene compound. However, none of the prior art is actually disclosing an elastomer having repeating units derived from at least one isomonoolefin monomer, at least one dusoalkenylbenzene monomer, and optionally further copolymerizable monomers, said elastomer having a Mooney viscosity (ML 1+8@125 °C according to ASTM D1646) of more than 80 units.

SUMMARY The present invention relates to an elastomer having repeating units derived from at least one isomonoolefin monomer, at least one dusoalkenylbenzene monomer, and optionally further copolymerizable monomers, said elastomer having a Mooney viscosity (ML 1+8@125 °C according to ASTM D1646) of more than 80 units and to a process of obtaining said elastomer via a direct cationic reaction of at least one isomonoolefin monomer, at least one dusoalkenylbenzene monomer, and optionally further co-monomers. At the same time, a predominant portion (> 50 %) of said elastomer is soluble in a hydrocarbon solvent, such as cyclohexane under reflux for 60 min. This modified butyl-type rubber has fully saturated main polymer chains and is curable with sulfur curing agents. It is useful in applications where other types of very high Mooney viscosity rubber are being used which do not display advantages typical for butyl polymer or polyisobutylene, such as e.g., NBR elastomers.

DETAILLED DESCRIPTION OF THE INVENTION The present invention preferably relates to butyl-like polymers. The terms "butyl rubber", "butyl polymer" and "butyl rubber polymer" are used throughout this specification interchangeably. While the prior art in using butyl rubber refers to polymers prepared by reacting a monomer mixture comprising a C₄ to C₇ isomonoolefin monomer and a C₄ to C₁₄ multiolefin monomer or β-pinene, this invention relates to elastomeric polymers comprising repeating units derived from at least one isomonoolefin monomer, at least one dusoalkenylbenzene monomer, and optionally further copolymerizable monomers, said elastomer having a Mooney viscosity (ML 1+8@125 °C according to ASTM D1646) of more than 80 units. Preferred are elastomeric polymers comprising repeating units derived from at least one isomonoolefin monomer and at least one dusoalkenylbenzene monomer, which due to the lack of further comonomers, such as multiolefin monomer/conjugated aliphatic diene or β-pinene, have no double-bonds in the polymer chains. The present invention is not restricted to any particular isomonoolefin monomer, however C₄ to C₇ isomonoolefin monomers are preferred. Preferred C₄ to C monoolefins are isobutylene, 2-methyl-l -butene, 3 -methyl- 1 -butene, 2-methyl-2- butene, 4-methyl-l-pentene and mixtures thereof. The most preferred isomonoolefin monomer is isobutylene. The present invention is not restricted to any particular dusoalkenylbenzene provided that the dusoalkenylbenzene is copolymerisable with the isoolefin monomer(s) present. Examples of suitable diisoalkenylbenzenes are the meta- or para- isomers of diisopropenylbenzene and dimethallylbenzene. The monomer mixture preferably comprises no multiolefin monomers, such as isoprene, butadiene, 2-methy -butadiene, 2,4-dimethylbutadiene, piperyline, 3-methyl-

1,3-pentadiene, 2,4-hexadiene, 2-neopentylbutadiene, 2-methyl-l,5-hexadiene, 2,5- dimethyl-2,4-hexadiene, 2-methyl- 1 ,4-pentadiene, 2-methyl- 1 , 6-heptadiene, cyclopenta-diene, methylcyclopentadiene, cyclohexadiene, 1-vinyl-cyclohexadiene. Preferably, the monomer mixture to be polymerized comprises in the range of from 65 % to 99.99 % by weight of at least one isomonoolefin monomer and in the range of from 0.01 % to 35 % by weight of at least one dusoalkenylbenzene monomer or a mixture thereof. More preferably, the monomer mixture comprises in the range of from 85 % to 99.95 % by weight of a C₄ to C₇ isomonoolefin monomer, in the range of from 0.05 % to 15 % by weight of at least one dusoalkenylbenzene compound or a mixture thereof. In case there are further copolymerizable comonomers, it will be apparent to the skilled in the art that the ranges given above will change and result in a total of all monomers of 100 % by weight. The monomer mixture may contain minor amounts of one or more additional polymerizable co-monomers. For example, the monomer mixture may contain a small amount of a styrenic monomer. Preferred styrenic monomers are p-methylstyrene, styrene, α-methyl-styrene, p-chlorostyrene, p-methoxystyrene, indene (including indene derivatives) and mixtures thereof. If present, it is preferred to use the styrenic monomer in an amount of up to 5.0% by weight of the monomer mixture. The values of the isomonoolefin monomer(s) will have to be adjusted accordingly to result again in a total of 100 % by weight. The use of even other monomers in the monomer mixture is possible provided, of course, that they are copolymerizable with the other monomers in the monomer mixture. The inventive polymer has a Mooney viscosity ML (1+8 @125 °C) of greater than 80, preferably greater than 90, more preferably greater than 95 units. The elastomer of the present invention is prepared by a cationic process for polymerising the monomer mixture. This type of polymerisation is well known to the skilled in the art and usually comprises contacting the reaction mixture described above with a catalyst system. Preferably, the polymerization is conducted at a temperature conventional in the production of butyl polymers - e.g., in the range of from -100°C to +50°C. The polymer may be produced by polymerization in solution or by a slurry polymerization method. Polymerization is preferably conducted in suspension (the slurry method) - see, for example, Ullmann's Encyclopedia of Industrial Chemistry (Fifth, Completely Revised Edition, Volume A23 ; Editors Elvers et al, 290-292). As an example, in one embodiment the polymerization is conducted in the presence of an inert aliphatic hydrocarbon diluent (such as n-hexane) and a catalyst mixture comprising a major amount (in the range of from 80 to 99 mole percent) of a dialkylaluminum halide (for example diethylaluminum chloride), a minor amount (in the range of from 1 to 20 mole percent) of a monoalkylalummum dihalide (for example isobutylaluminum dichloride), and a minor amount (in the range of from 0.01 to 10 ppm) of at least one of a member selected from the group comprising water, aluminoxane (for example methylaluminoxane) and mixtures thereof. Of course, other catalyst systems conventionally used to produce butyl polymers can be used to produce a butyl polymer which is useful herein - see, for example, "Cationic Polymerization of Olefins: A Critical Inventory" by Joseph P. Kennedy (John Wiley & Sons, Inc. © 1975, 10-12). Polymerization may be performed both continuously and discontinuously. In the case of a continuous operation, the process is preferably performed with the following three feed streams: I) solvent/diluent + isomonoolefin(s) (preferably isobutene) II) dusoalkenylbenzene monomer(s), and optionally, other copolymerizable monomers e.g., p-methylstyrene III) catalyst In the case of discontinuous operation, the process may, for example, be performed as follows: The reactor, pre-cooled to the reaction temperature, is charged with solvent or diluent and the reactants. The initiator is then pumped in the form of a dilute solution in such a manner that the heat of polymerization may be dissipated without problem. The course of the reaction may be monitored by means of the evo- lution of heat. The inventive polymer may be compounded. The compound comprises the inventive polymer and at least one active or inactive filler. The filler is preferably: - highly dispersed silicas, prepared e.g., by the precipitation of silicate solutions or the flame hydrolysis of silicon halides, with specific surface areas of in the range of from 5 to 1000 m²/g, and with primary particle sizes in the range of from 10 to 400 nm; the silicas can optionally also be present as mixed oxides with other metal oxides such as those of Al, Mg, Ca, Ba, Zn, Zr and Ti; - synthetic silicates, such as aluminum silicate and alkaline earth metal silicate like magnesium silicate or calcium silicate, with BET specific surface areas in the range of from 20 to 400 m²/g and primary particle diameters in the range of from 10 to 400 nm; - natural silicates, such as kaolin and other naturally occurring silica; - glass fibres and glass fibre products (matting, extradates) or glass microspheres; - metal oxides, such as zinc oxide, calcium oxide, magnesium oxide and aluminum oxide; - metal carbonates, such as magnesium carbonate, calcium carbonate and zinc carbonate; - metal hydroxides, e.g. aluminum hydroxide and magnesium hydroxide; - carbon blacks; the carbon blacks to be used here are prepared by the lamp black, furnace black or gas black process and have preferably BET (DIN 66 131) specific surface areas in the range of from 20 to 200 m²/g, e.g. SAF, ISAF, HAF, FEF or GPF carbon blacks; - rubber gels, especially those based on polybutadiene, butadiene/styrene copolymers, butadiene/acrylonitrile copolymers and polychloroprene; or mixtures thereof. Examples of preferred mineral fillers include silica, silicates, clay such as bentonite, gypsum, alumina, titanium dioxide, talc, mixtures of these, and the like. These mineral particles have hydroxyl groups on their surface, rendering them hydrophilic and oleophobic. This exacerbates the difficulty of achieving good interaction between the filler particles and the tetrapolymer. For many purposes, the preferred mineral is silica, especially silica made by carbon dioxide precipitation of sodium silicate. Dried amorphous silica particles suitable for use in accordance with the invention may have a mean agglomerate particle size in the range of from 1 to 100 microns, preferably between 10 and 50 microns and most preferably between 10 and 25 microns. It is preferred that less than 10 percent by volume of the agglomerate particles are below 5 microns or over 50 microns in size. A suitable amorphous dried silica moreover usually has a BET surface area, measured in accordance with DIN (Deutsche Industrie Norm) 66131, of in the range of from 50 and 450 square meters per gra and a DBP absorption, as measured in accordance with DIN 53601, of in the range of from 150 and 400 grams per 100 grams of silica, and a drying loss, as measured according to DIN ISO 787/11, of in the range of from 0 to 10 percent by weight. Suitable silica fillers are available under the trademarks HiSil® 210, HiSil® 233 and HiSil® 243 from PPG Industries Inc. Also suitable are Vulkasil® S and Vulkasil® N, from Bayer AG. It might be advantageous to use a combination of carbon black and mineral filler in the inventive compound. In this combination the ratio of mineral fillers to carbon black is usually in the range of from 0.05 to 20, preferably 0.1 to 10. For the rubber composition of the present invention it is usually advantageous to contain carbon black in an amount of in the range of from 20 to 200 parts by weight, preferably 30 to 150 parts by weight, more preferably 40 to 100 parts by weight. The compound further comprises at least one curing system, such as a sulfur curing system. The invention is not limited to a special sulfur curing system. For further reference, see, chapter 2, "The Compounding and Vulcanization of Rubber", of "Rubber Technology", 3^rd edition, published by Chapman & Hall, 1995, the disclosure of which is incorporated by reference with regards to jurisdictions allowing for this procedure. The preferred amount of sulfur is from 0.3 to 2.0 parts by weight per hundred parts of rubber. An activator, for example zinc oxide, may also be used, in an amount of from 5 parts to 2 parts by weight. Other ingredients, for instance stearic acid, antioxidants, or accelerators may also be added to the elastomer prior to curing. Sulphur curing is then effected in known manner. Even if it is not preferred, the compound may further comprise other natural or synthetic rubbers such as BR (polybutadiene), ABR (butadiene/acrylic acid-Ci-Czj.- alkylester-copolymers), CR (polychloroprene), IR (polyisoprene), SBR (styrene/butadiene-copolymers) with styrene contents in the range of 1 to 60 wt%, NBR (butadiene/acrylonitrile-copolymers with acrylonitrile contents of 5 to 60 wt%, HNBR (partially or totally hydrogenated NBR-rabber), EPDM (ethylene/propylene/diene- copolymers), FKM (fluoropolymers or fluororubbers), and mixtures of the given polymers. The compound described herein above can contain further auxiliary products for rubbers, such as reaction accelerators, vulcanizing accelerators, vulcanizing acceleration auxiliaries, antioxidants, foaming agents, anti-aging agents, heat stabilizers, light stabilizers, ozone stabilizers, processing aids, plasticizers, tackifiers, blowing agents, dyestuffs, pigments, waxes, extenders, organic acids, inhibitors, metal oxides, and activators such as triethanolamine, polyethylene glycol, hexanetriol, etc., which are known to the rubber industry. The rubber aids are used in conventional amounts, which depend inter alia on the intended use. Conventional amounts are e.g. from 0.1 to 50 wt.%, based on rubber. Preferably the composition furthermore comprises in the range of 0.1 to 20 phr of an organic fatty acid, preferably an unsaturated fatty acid having one, two or more carbon double bonds in the molecule which more preferably includes 10% by weight or more of a conjugated diene acid having at least one conjugated carbon-carbon double bond in its molecule. Preferably those fatty acids have in the range of from 8 to 22 carbon atoms, more preferably 12- 18. Examples include stearic acid, palmic acid and oleic acid and their calcium-, zinc-, magnesium-, potassium- and ammonium salts. The ingredients of the final compound are mixed together, suitably at an elevated temperature that may range from 25 °C to 200 °C. Normally the mixing time does not exceed one hour and a period of time from 2 to 30 minutes is usually adequate. The mixing is suitably carried out in an internal mixer such as a Banbury mixer, or a Haake or Brabender miniature internal mixer. A two roll mill mixer also provides a good dispersion of the additives within the elastomer. An extruder also provides good mixing, and permits shorter mixing times. It is possible to carry out the mixing in two or more stages, and the mixing can be done in different mixing devices, for example the first stage in an internal mixer and the second one in an extruder. However, it is important that no unwanted pre-crosslinking (= scorch) occurs during the mixing stage. For compounding and vulcanization see also: Encyclopedia of Polymer Science and Engineering, Vol. 4, p. 66 et seq. (Compounding) and Vol. 17, p. 666 et seq. (Vulcanization). The polymer prepared according to the inventive method and a compound comprising said polymer is useful for the manufacture of shaped rubber parts, such as printing rollers, containers, tubes and bags for non-medical applications, parts of electronic equipment, in particular insulating parts, parts of containers containing electrolytes, rings, dampening devices, seals and sealants or shaped rubber parts either solid, foamed, or fluid-filled useful to isolating vibrations and dampening vibrations generated by mechanical devices. The invention is further illustrated by the following examples.

Examples Methyl chloride (Dow Chemical) serving as a diluent for polymerization and isobutylene monomer (Matheson, 99 %) were transferred into a reactor by condensing a vapor phase. Aluminum chloride (99.99 %) was from Aldrich and used as received. Commercial divinylbenzene (ca. 64 %) was from Dow Chemical. It was purified using a disposable inhibitor-removing column from Aldrich. The mixing of a compound with carbon black (IRB #7) and peroxide (DI-CUP 40C, Struktol Canada Ltd.) was done using a miniature internal mixer (Brabender MIM) from C. W. Brabender equipped with a drive unit (Plasticorder^® Type PL-V151). The Mooney viscosity test was carried out according to ASTM standard D-1646 on a Monsanto MV 2000 Mooney Viscometer ML (1+8 @ 125 deg.C). The Moving Die Rheometer (MDR) test was performed according to ASTM standard D-5289 on a Monsanto MDR 2000 (E). The upper die oscillated through a small arc of 1 degree. The solubility of a polymer was determined after the sample refluxed in cylohexane over 60-minute period. Curing was done using an Electric Press equipped with an Allan-Bradley Programmable Controller. Stress-strain tests were carried out using the Instron Testmaster Automation System, Model 4464.

Examples 1-3 (comparative) Three different samples of commercial crosslinked IB-IP-DVB terpolymer (XL- 10000™) obtained from Bayer Inc. were tested for Mooney viscosity and solubility (Table 1).

Table 1. Mooney viscosity and solubility values for three commercial samples of XL- 10000.

These three different terpolymers with Mooney viscosity values between 60-80 units had a content of a soluble fraction in a hydrocarbon solvent below 30 wt.%. Higher values of Mooney viscosity seem to be accompanied by lower values of a polymer fraction soluble in a hydrocarbon solvent.

Example 4 (comparative) To a 250 mL Erlenmeyer flask, 0.45 g of A1C1₃ was added, followed by 100 mL of methyl chloride at - 30 °C. The resulting solution was stirred for 30 min at - 30 °C and then cooled down to - 95 °C, thus forming the catalyst solution. To a 2000 mL glass reactor equipped with an overhead stirrer, 900 mL of methyl chloride at - 95 °C was added, followed by 120.0 mL of isobutylene at - 95 °C and 4.8 mL of DVB (ca. 64 %) at room temperature. The reaction mixture was brought to - 95 °C and 10 mL of the catalyst solution was added to start the reaction. The polymerization was carried out in MBRAUN^® dry box under the atmosphere of dry nitrogen. The reaction was terminated after 10 minutes by adding into the reaction mixture 10 mL of ethanol containing some sodium hydroxide. The obtained product was steam coagulated and dried to a constant weight in the vacuum oven at 70 °C. The yield of the reaction was 96.1 %. The solubility of the rubber in cyclohexane was 32.9 %. It was found that a crosslinking process took place during the Mooney viscosity test for this rubber. The final value obtained form this test was 41.7 units (on a scorched polymer) while the lowest value of MV recorded before the onset of crosslinking was 32.0 units.

Example 5 The reaction described in Example 4 was repeated except that divinylbenzene in the monomer feed was replaced with 3.84 mL of m-diisopropenylbenzene. This way, the molar amounts of neat DVB (Example 4) and m-diisopropenylbenzene (Example 5) were equal. The yield of the reaction was 97.6 %. The solubility of the rubber in cyclohexane was 82.4 %. The Mooney viscosity of this product was 60.8 units. No scorch was observed during the Mooney viscosity test. Comparison of results from the Examples 4 and 5 is given in Table 2.

Table 2. Comparison of Mooney viscosity and solubility values of two isobutylene- containing copolymers described in Examples 4 and Example 5.

These results indicated that under the above-given reaction conditions the copolymer isobutylene-(m-diisopropenylbenzene) had a much higher Mooney viscosity and solubility than the analogous copolymer composed of isobutylene and divinylbenzene.

Example 6 To a 250 mL Erlenmeyer flask, 0.63 g of A1C1₃ was added, followed by 140 mL of methyl chloride at - 30 °C. The resulting solution was stirred for 30 min at - 30 °C and then cooled down to - 95 °C, thus forming the catalyst solution. To a 2000 mL glass reactor equipped with an overhead stirrer, 900 mL of methyl chloride at - 95 °C was added, followed by 120.0 mL of isobutylene at - 95 °C and 15.0 mL of m-diisopropenylbenzene at room temperature. The reaction mixture was brought to - 95 °C and 20 mL of the catalyst solution was added to start the reaction. The polymerization was carried out in MBRAUN^® dry box under the atmosphere of dry nitrogen. The reaction was terminated after 30 minutes by adding into the reaction mixture 10 mL of ethanol containing some sodium hydroxide. The obtained product was steam coagulated and dried to a constant weight in the vacuum oven at 70 °C. The yield of the reaction was 95.3 %. The solubility of the rubber in cyclohexane was 54.6 %. The Mooney viscosity of this elastomer was 102.7 units. This demonstrated that this butyl-type rubber had a very high Mooney viscosity despite the fact that a predominant portion of it was soluble in a hydrocarbon solvent. This behavior is different from that known for commercial XL- 10000™ terpolymers.

Example 7 The polymer described in Example 6 (Polymer 6) was compounded using the following recipe:

Polymer: 100 phr Carbon black N330™ (available from Cabot Canada): 50 phr Stearic acid (Emersol™ 132 NF) (available from H. M. Royal): 1.0 phr Zinc oxide (Kadox® 920) (from St. Lawrence Chem. Co. Ltd.): 3.0 phr Sulfur NBS (available from National Bureau of Standards): 1.75 phr Methyl Tuads (TMTD) (available from R. T. Vanderbilt): 1.0 phr

The mixing was done in a Brabender internal mixer (capacity ca. 75 cc). The starting temperature was 60 °C and the mixing speed 50 rpm. The following steps were carried out: 0 min: polymer added, followed by carbon black and stearic acid 3 min: sweep (during mixing of carbon black with the polymer and other powdery materials it is unavoidable that small pieces of carbon black and other powders fall off the rolls of a mill or from a mixing chamber of an internal mixer. There is usually a metal tray under a mixer - and with a small brush these fallen pieces are carefully sweeped and then added again on the mill or into the mixing chamber - this step assures that all intended ingredients are added to the compound without any losses.) 3.5 min: ZnO added, followed by sulfur and TMTD 7 min: mix removed The compound was passed six times through a mill (6"xl2") with a tight nip gap- The obtained compound was tested using the Moving Die Rheometer (MDR). Also, after curing at 160 °C it was tested for stress-strain properties. The results are given in Table 3.

Table 3. MDR and some stress-strain characteristics for a sulfur-cured compound based on Polymer 6.

These results demonstrated that copolymers IB-(m-Di-IPB) could be vulcanized with sulfur curing systems.

Claims

Claims:

1. An elastomer having repeating units derived from at least one isomonoolefin monomer, at least one dusoalkenylbenzene monomer, and optionally further copolymerizable monomers, said elastomer having a Mooney viscosity (ML 1+8@125 °C according to ASTM D1646) of more than 80 units.

2. An elastomer according to claim 1, wherein the isomonoolefin monomer(s) are selected from the group consisting of isobutylene, 2-methyl- 1 -butene, 3-methyl- 1 -butene, 2-methyl-2 -butene, 4-methyl- 1 -pentene and mixtures thereof.

3. An elastomer according to claim 1 or 2, wherein the dusoalkenylbenzene compound is a m- or p-diisopropenylbenzene, m- or p-dimethallylbenzene or mixture thereof.

4. A compound comprising an elastomer according to any of claim 1 to 3, at least one filler and at least one curing system.

5. A compound comprising an elastomer according to according to claim 1 wherein the curing system is a sulfur curing system.

6. A cationic polymerization process for manufacturing an elastomer according to any of claim 1 to 3 wherein the monomers are polymerized in the presence of a catalyst.